JP5419966B2 - Plasticizer-containing sheet comprising polyvinyl acetal having cyclohexane-1,2-dicarboxylic acid ester as a plasticizer - Google Patents

Description

  The present invention relates to a plasticizer-containing, partially acetalized polyvinyl alcohol-based sheet using hydrogenated phthalate ester as a plasticizer, suitable as an intermediate layer in laminated safety glass, and laminated glass and The use of an intermediate layer in a photovoltaic module.

BACKGROUND ART Laminated safety glass is generally composed of two glass plates and an intermediate sheet bonded to the glass plates. As the sheet material, a plasticizer-containing partially acetalized polyvinyl alcohol (polyvinyl acetal), particularly polyvinyl butyral (PVB) is used. Laminated safety glass (VSG) is used, for example, as a windshield or side glass in the automotive field and as a safety glass in the building field.

As a plasticizer for such a PVB sheet, an aliphatic diester of tri- or tetraethylene glycol is fixed therebetween. Most often, 3G7, 3G8 or 4G7 is used as a plasticizer, where the first number represents the number of ethylene glycol units and the last number represents the number of carbon atoms in the carboxylic acid moiety of the compound. Thus, 3G8 is triethylene glycol - bis - (2-ethylhexanoate), namely formula _{C 4 H 9 CH (CH 2} CH 3) CO (OCH 2 CH 2) 3 O 2 CCH (CH 2 CH ₃ ) Represents a compound of C ₄ H ₉ .

  As a plasticizer for partially acetalized polyvinyl alcohol, a compound that advantageously provides high transparency, low moisture absorption, good adhesion to glass and sufficient cold flexibility of the sheet in the VSG interlayer sheet Is used. Furthermore, the compound must have sufficient compatibility with the partially acetalized polyvinyl alcohol, ie it can be mixed with the partially acetalized polyvinyl alcohol without leaching again in a sufficient amount Must.

  In general, the compatibility between the plasticizer and the partially acetalized polyvinyl alcohol decreases with a decrease in the polar properties of the plasticizer. A relatively high polarity plasticizer is more compatible with polyvinyl acetal than a plasticizer having a relatively low polarity. Apart from that, the compatibility of relatively low polarity plasticizers increases with increasing degree of acetalization, ie with decreasing number of hydroxyl groups and thus with decreasing polarity of polyvinyl acetal.

  In EP 0877 665 B1, low polarity 3G8 is recommended as a plasticizer for PVB sheets, as this gives the sheet product improved moisture resistance. During the production of laminated safety glass (VSG) with PVB sheets, moisture continuously impairs the adhesion between the adhesive sheet and the glass, and in extreme cases, the sheet peels off from the glass. In addition, the sheet should be as moisture resistant as possible.

  This improved moisture resistance of PVB sheets plasticized with 3G8 results from the highly non-polar character of this plasticizer compared to plasticizers such as 4G7 or 3G7, because heptane This is because the octanoic acid group instead of the acid ester chemically forms this plasticizer molecule. A further advantage when using 3G8 is its relatively low volatility, which on the one hand counteracts the decrease in plasticizer concentration at the exposed edges of the VSG and on the other hand when processing the sheet to VSG. This is because a low odor burden is realized.

  For this reason, the plasticizer 3G8 has been fixed in the PVB sheet manufacturer in a short period of time.

  On the other hand, the outstanding technical characteristics of this product, however, are significantly higher compared to the standard plasticizers popular in other industrial fields, for example phthalates used in PVC plasticizers. Cost or manufacturing cost is an obstacle. In addition, further reduction in moisture absorption of the plasticized PVB sheet is desirable because it further improves the shelf life of the laminated safety glass. There is a limit to this further reduction in moisture absorption in the case of 3G8 due to the highly hydrophilic proportion of triethylene glycol.

  From EP O 877 665 B1, it is known that a plasticizer exudation is expected, so that a PVB type with a polyvinyl alcohol content higher than 19.5% by weight cannot be easily plasticized with 3G8 It is. As with other plasticizer-containing plastic products, this plasticizer exudation is undesirable even in the case of an interlayer sheet for VSG, since the release of plasticizer is notably PVB at the edge of the composite material. This is because delamination is caused too fast along the exposed edge of the film. Due to this low compatibility or the tendency of 3G8 to exude, EP 0877 665 B1 limits the use of 3G8 to PVB types having a polyvinyl alcohol content of 17 to 19.5% by weight.

  As a rule, the lack of compatibility of the plasticizer / PVB mixture is that other nonpolar plasticizers such as dialkyl adipates having more than 6 carbon atoms in the ester alcohol, more than 4 carbon atoms in the ester alcohol. This also applies to dialkyl sebacate or phthalate plasticizers having, for example, dioctyl phthalate or diisononyl phthalate. In the case of a lack of compatibility, leaching of the plasticizer is also observed, especially when stored in wet and / or cold environments. Both of these environmental conditions actually occur during the use of PVB sheets and are therefore important for the evaluation of plasticizer compatibility.

  PVB-wrapped sheets are usually stored and transported at temperatures below 8 ° C. in order to suppress adhesion with adjacent sheet layers. In this case, of course, it is not desirable for the liquid plasticizer to leach out of the sheet during storage.

  In addition, laminated safety glass made with PVB sheets is assembled and exposed to low temperatures and high humidity depending on weather conditions, which is inadequate compatibility Especially at the edge of the VSG where the PVB sheet is exposed, it causes a chronic loss of plasticizer, which in turn causes obvious defects in the form of bubbles or delamination of the sheet from the glass.

  Except for a slight compatibility, relatively low polarity plasticizers reduce the cold flexibility of PVB sheets in combination with appropriate PVB compared to relatively high polarity plasticizers such as 3G7. Has the property of causing This is especially true when the plasticizer content is adjusted to less than 25% and / or when the polyvinyl butyral used has a low degree of acetalization and thus has a high residual content of polyvinyl alcohol groups. Arise. In other words, when the degree of acetalization is too low, the softening temperature (Tg) of PVB increases, which adversely affects the cold flexibility of the plasticizer-containing sheet produced thereby.

  DE 101 16812 A1 proposes the use of derivatives of cyclohexane polycarboxylic acid esters for the plasticization of PVC and PVB. In this case, the mixing with polyvinyl butyral in which the proportion of free hydroxyl groups is in the range of 5 to 50% is described. Depending on the type and distribution of cyclic acetal, hydroxyl and acetate groups, the polyvinyl butyral has a softening temperature Tg of at least 80 ° C.

  The content of polyvinyl acetal with respect to the total mixture is 5 to 95% by weight, in particular 20 to 55% by weight. For this plasticizer content, this corresponds to a numerical range of 5 to 95% by weight, or 45 to 80% by weight, assuming that no other components are added.

  Incompatibility occurs at high plasticizer proportions when using PVB with a softening temperature above 80 ° C. If the plasticizer proportion is reduced, low cold flexibility of the sheet results.

Technical challenges Can be procured at low cost, produce low moisture absorption in the sheet compared to 3G8, and are compatible and good in combination with partially acetalized polyvinyl alcohol with a sufficiently high degree of acetalization There arises a need to prepare PVB sheets under the use of plasticizers that produce sheets with good cold flexibility.

TECHNICAL SOLUTION Sheets containing polyvinyl butyral having a low softening temperature (Tg), softened with a diester of 1,2-cyclohexanedicarboxylic acid, have lower moisture absorption compared to sheets with 3G8 as a softening agent. It was found to have. Sheets of this composition have good plasticizer compatibility and good cold flexibility.

DESCRIPTION OF THE INVENTION Accordingly, the subject of the present invention is 10 to 90% polyvinyl acetal having a softening temperature lower than 74 ° C. and 10 to at least one cyclohexanedicarboxylic acid ester having 4 to 17 C atoms in the ester group. It is a plasticizer-containing sheet containing -40% by mass (relative to the total formulation of the sheet).

  As cyclohexanedicarboxylic acid esters, all compounds described in DE 101 16 812 can be used.

  For reasons of easy availability, hydrogenated diesters of phthalic acid, ie hydrogenated diesters of 1,2-cyclohexanedicarboxylic acid, are the preferred plasticizers of the present invention.

  As ester alcohols, in particular ester alcohols having 9 to 17 carbon atoms, particularly preferably ester alcohols having 9, 13 or 17 carbon atoms (so-called oxo alcohols) are used. These alcohols may be used either branched or unbranched, in which case the use of a sufficiently unbranched ester alcohol gives a better plasticizing action.

Cyclohexanedicarboxylic acid ester plasticizers that are used by the present invention, at least one other non-polar or polar, added in combination with a plasticizer suitable as a plasticizer, be used in a proportion of 1 to 40% Can do.

  Advantageously, the sheet has a total plasticizer content in the sheet in the range of 10 to 40% by weight, 14 to 32% by weight, 16 to 30% by weight, 18 to 28% by weight, in particular 22 to 26% by weight. That is, it has a proportion of all plasticizers. The proportion of cyclohexanedicarboxylate plasticizer used according to the invention is more than 10%, more than 20%, more than 30%, more than 40% and more than 50% for this mixture. , Over 60%, over 70%, over 80%, or over 90%.

Basically, the sheet may contain a plasticizer mixture consisting of the aforementioned cyclohexanedicarboxylate plasticizer and at least one of the following plasticizers known for PVB:
Esters of polyvalent aliphatic or aromatic acids, such as dialkyl adipates, such as dihexyl adipate, dioctyl adipate, hexyl cyclohexyl adipate, mixtures of heptyl adipate and nonyl adipate, heptylnonyl adipate and adipine Esters of acids and ester alcohols having cycloaliphatic or ether linkages, dialkyl sebacates such as dibutyl sebacate and esters of sebacic acid and ester alcohols containing cycloaliphatic or ether linkages, esters of phthalic acid, For example, butyl benzyl phthalate or bis-2-butoxyethyl phthalate.
An ester or ether of a polyhydric aliphatic or aromatic alcohol or an oligoether glycol having one or several unbranched or branched aliphatic or aromatic substituents, such as di-, tri- or tetra Esters of glycols with linear or branched aliphatic or cycloaliphatic carboxylic acids; examples for the latter group include diethylene glycol bis- (2-ethylhexanoate), triethylene glycol bis- ( 2-ethylhexanoate), triethylene glycol-bis- (2-ethylbutanoate), tetraethylene glycol-bis-n-heptanoate, triethylene glycol-bis-n-heptanoate, triethylene glycol-bis-n Hexanoate, tetraethylene glycol-dimethyl ether and / or Dipropylene glycol benzoate.

  Suitable additive plasticizers for this group having a relatively high polarity include, for example, di- (2-butoxyethyl) -adipate (DBEA), di- (2-butoxyethyl) -sebacate (DBES), di- (2-butoxyethyl) -azelate, di- (2-butoxyethyl) -glutarate. Di- (2-butoxyethoxyethyl) -adipate (DBEEA), di- (2-butoxyethoxyethyl) -sebacate (DBEES), di- (2-butoxyethoxyethyl) -azelate, di- (2-butoxyethoxyethyl) ) -Glutarate, di- (2-hexoxyethyl) -adipate, di- (2-hexoxyethyl) -sebacate, di- (2-hexoxyethyl) -azelate, di- (2-hexoxyethyl) -glutarate, di- (2-hex) Soxyethoxyethyl) -adipate, di- (2-hexoxyethoxyethyl) sebacate, di- (2-hexoxyethoxyethyl) -azelate, di- (2-hexoxyethoxyethyl) -glutarate, di- (2- Butoxyethyl) -phthalate and / or di- (2-butoxyethoxy) Chill) - phthalate. Similarly, nonionic surfactants can be used.

In order not to unnecessarily deteriorate the moisture resistance of this sheet by the use of too polar plasticizers in the mixture, particularly low polarity plasticizers can be combined with the cyclohexanedicarboxylic esters used according to the invention. As a plasticizer having a relatively low polarity, a plasticizer having a polarity of 9.4 or less calculated by the formula 100 × (number of O atoms) / (number of C atoms + number of H atoms) is valid. As relatively low polarity plasticizers, dialkyl adipates having alkyl groups with more than 6 carbon atoms and oligoglycolates having carboxylic acid groups with more than 7 carbon atoms are preferably used. In particular, the following compounds are suitable:
Table 1

  Further, the sheet according to the present invention is made of other additives known to those skilled in the art, such as residual water, UV absorbers, antioxidants, tackifiers, optical brighteners, stabilizers, colorants, processing aids, Organic or inorganic nanoparticles, pyrolytic silicic acid and / or surfactants can be included.

  With the use of the above plasticizers or plasticizer combinations, it is possible to produce sheets with a particularly low plasticizer release, which reduces the odor burden or plasticizer aerosols during further processing. Provides the advantage of increased storage stability in manufactured VSG.

  Advantageously, the plasticizer release (defined below) of the sheet according to the invention is at least less than 4% by weight, preferably less than 3% by weight, particularly preferably less than 2% by weight, most preferably relative to the total sheet. It is preferably less than 1% by weight.

  Preferably, the partially acetalized polyvinyl alcohol has a polyvinyl acetal content (degree of acetalization) of 81% by weight or more, preferably 82% by weight or more, particularly preferably 83% by weight or more, in particular 84% by weight or more. Acetalized or partially butyralized polyvinyl alcohol (polyvinyl butyral) is used, since this partially acetalized polyvinyl alcohol has a sufficiently low softening temperature and polarity and good cooling. This is to produce a preparation which is compatible with the cyclohexanedicarboxylic acid ester plasticizer having interstitial flexibility. However, it is not preferred to exceed a degree of acetalization of 87% by weight, since the mechanical properties of the sheet are generally no longer sufficient. In a particularly advantageous variant of the invention, this degree of acetalization is 81 to 87, 82 to 86, 83 to 85.5% by weight with about 1% by weight of residual acetate. In the case of relatively high residual acetate contents exceeding 1% by weight, the figures for the degree of acetalization are correspondingly reduced.

  The sum of the degree of acetalization and the residual acetate can be calculated as a fraction lacking 100 from the polyvinyl alcohol content measured by ASTM D 1396, that is, as the proportion of free hydroxyl groups in the polyvinyl acetal. This degree of acetalization can also be determined directly by high resolution NMR spectroscopy.

  Since the sheets according to the invention have sufficient cold flexibility and at the same time sufficient mechanical strength at elevated temperatures, the polyvinyl acetals which can be used for the present invention are basically below 74 ° C., preferably 64 It has a softening temperature (Tg) in the range of -74 ° C, preferably 65-73 ° C, particularly preferably 66-72 ° C, especially 67-71 ° C.

  For the production of polyvinyl acetal, polyvinyl alcohol is dissolved in water and acetalized using an aldehyde, such as butyraldehyde, with the addition of an acid catalyst. The resulting polyvinyl acetal is separated, washed neutral, suspended in an aqueous medium optionally adjusted to alkaline, then washed again neutral and dried.

  The polyvinyl alcohol content of the polyvinyl acetal can be adjusted by the amount of aldehyde used in the acetalization. Acetalization can also be carried out with other or multiple aldehydes having 2 to 10 carbon atoms (eg valeraldehyde).

  Sheets based on plasticizer-containing polyvinyl acetal preferably contain uncrosslinked polyvinyl butyral (PVB), which is obtained by acetalization of polyvinyl alcohol with butyraldehyde.

  The use of cross-linked polyvinyl acetals, in particular cross-linked polyvinyl butyral (PVB), is likewise possible. Suitable crosslinked polyvinyl acetals are, for example, EP 1527107 B1 and WO 2004/063231 A1 (thermal self-crosslinking of carboxyl-containing polyvinyl acetals), EP 1606325 A1 (polyaldehyde crosslinked polyvinyl acetals) and WO 03 / 020776 A1 (polyvinyl acetal crosslinked with glyoxylic acid). The disclosures of these patent applications are incorporated herein by reference in their entirety.

  As polyvinyl alcohol, it is also possible within the scope of the present invention to use terpolymers consisting of hydrolyzed vinyl acetate / ethylene copolymers. This compound is generally 98% or more hydrolyzed and contains 1 to 10% by weight of ethylene-based units (eg type “Exceval” from Kuraray Europe GmbH).

  As polyvinyl alcohol, it is also possible within the scope of the present invention to use hydrolyzed copolymers consisting of vinyl acetate and at least one other ethylenically unsaturated monomer.

  This polyvinyl alcohol can be used within the scope of the present invention as pure polyvinyl alcohol or as a mixture of polyvinyl alcohols having various degrees of polymerization or hydrolysis.

  Polyvinyl acetal contains units derived from vinyl acetate and vinyl alcohol in addition to acetal units. In general, the polyvinyl alcohol content of the partially acetalized polyvinyl alcohol used is between 12 and 18%, preferably between 13 and 16%, most preferably between 14 and 16%.

  The residual acetate content of the polyvinyl acetals used according to the invention is generally less than 5% by weight, preferably less than 3% by weight, particularly preferably less than 2% by weight, in particular less than 1.5% by weight or less than 1% by weight. .

  The principle production and composition of sheets based on polyvinyl acetal is described, for example, in EP 185 863 B1, EP 1 118 258 B1, WO 02/102591 A1, EP 1 118 258 B1 or EP 387 148 B1.

INDUSTRIAL APPLICABILITY The sheet according to the present invention can be used by laminating it with one or more glass plates by methods known to those skilled in the art, particularly for the production of laminated safety glass. This laminated safety glass can be used, for example, as a windshield in the automotive field, as a transparent member in the building field or in furniture. Based on the slight moisture absorption and plasticizer release of the sheet according to the invention, this is well suited for the production of glass / sheet / plastic laminates, for example for the continuous adhesion of glass plates with PET layers. Yes. Adhesion of two plastic plates, for example made of polycarbonate or PMMA, can also be carried out with the sheet according to the invention.

  The sheet according to the invention can be used for adhesion of photovoltaic modules.

Another subject of the invention is therefore
a) a transparent front cover;
b) one or more photosensitive semiconductor layers;
c) a laminate comprising a polyvinyl acetal-based sheet containing at least one plasticizer and d) a back cover, wherein the plasticizer-containing sheet has a softening temperature Tg of less than 74 ° C. It is a photovoltaic module containing 60 to 90% of polyvinyl acetal and 10 to 40% by mass of at least one cyclohexanedicarboxylic acid ester having 4 to 17 C atoms in the ester group as a plasticizer.

  For the photovoltaic modules according to the invention, all described variations of plasticizer-containing sheets or described variations of cyclohexanedicarboxylic acid esters can be used.

  Advantageously, the sheet used according to the invention is at least 5E + 11 ohm · cm or at least 1E + 12 ohm · cm, particularly preferably at least 5E + 12 ohm · cm or at least 1E + 13 ohm · cm or in particular at least 1E + 14 ohm at an ambient humidity of 85% rF at 23 ° C. -Has a specific resistance of cm. This value is preferably achieved at each point of the sheet, and in particular at the edge region of the module.

Furthermore, the ion mobility depending on the moisture content of the sheet and the specific resistance thereby can be influenced by the addition of SiO ₂ , in particular pyrolyzable silica. The sheet based on plasticizer-containing polyvinyl acetal used according to the invention preferably contains 0.001 to 15% by weight, preferably 2 to 5% by weight, of SiO ₂ .

  Avoiding trace amounts of acid during the manufacture of the sheet material makes it possible to reduce the tendency of the sheets used according to the invention to corrode against the light-sensitive semiconductor layer. This type of sheet is generally produced by extruding a plasticizer-containing polyvinyl acetal at elevated temperatures, which can cause thermal degradation of the polymeric material or plasticizer. Further, the water that has diffused and penetrated decomposes the residual acetate groups of the polyvinyl alcohol, thereby releasing acetic acid. In both cases, trace amounts of acid are generated that can attack the light-sensitive semiconductor layer.

  Advantageously, the sheets used according to the invention thus have a predetermined basicity, expressed as alkali titer, greater than 5 or 10, preferably greater than 15, particularly preferably greater than 20, 30 or 40. It is preferred not to exceed a maximum alkali titer of 100.

  This alkali titer is measured by back titration of the sheet as described below and is a basic substance, for example a metal salt of an organic carboxylic acid having 1 to 15 carbon atoms, in particular an alkali metal salt or alkaline earth Adjustments can be made by the addition of metal salts such as magnesium acetate or potassium acetate. This basic compound is usually used at a concentration of 0.005 to 2% by weight, in particular 0.05 to 1% by weight, based on the total mixture.

  Since the lamination of the photovoltaic modules takes place under the melting of this sheet, encapsulation of the photosensitive semiconductor layer using the sheet without bubbles and without fogging is obtained.

  In a variation of the photovoltaic module according to the invention, the light-sensitive semiconductor layer is provided on the cover d) (for example by vapor deposition, vapor deposition, sputtering, wet deposition) and is transparent by means of the sheet c). And glued.

  In other variations, this light-sensitive semiconductor layer is provided on a transparent front cover a) and bonded to the back cover d) by means of a sheet c).

  Alternatively, a photosensitive semiconductor layer can be embedded between the two sheets c) and glued to the covers a) and d).

  The thickness of the plasticizer-containing sheet based on polyvinyl acetal is mainly 0.38, 0.51, 0.76, 1.14, 1.52 or, when used for photovoltaic modules, 2.28 mm.

  The sheet used according to the invention fills the light-sensitive semiconductor layer or the hollow space present in this electrical connection during the lamination process.

  This transparent front cover a) is generally made of glass or PMMA. The cover d) (so-called backsheet) on the back side of the photovoltaic module according to the invention can be made of glass, plastic or metal or a composite material thereof, one of these supports being transparent Can do. Similarly, one or both covers can be configured as laminated glass (that is, as a laminate composed of at least two glass plates and at least one PVB sheet) or as insulating glass having a gas intermediate space. Of course, a combination of these techniques is also possible.

  The photosensitive semiconductor layer used in this module does not have to have special properties. A single crystal system, a polycrystalline system or an amorphous system can be used.

  In the case of a thin-layer solar module, this photosensitive semiconductor layer is provided directly on the carrier. Encapsulation is not possible in this case. Accordingly, a laminate comprising a carrier having a light-sensitive semiconductor layer (eg, a backside cover) and a transparent front cover is at least one intermediate layer based on a plasticizer-containing polyvinyl acetal. It is integrated by the sheet and thereby glued at an elevated temperature. Apart from this, a photosensitive semiconductor layer is provided on a transparent front cover as a carrier, the back cover and at least one invention in the middle based on a plasticizer-containing polyvinyl acetal. It can be adhered by a sheet.

  For the lamination of the laminate thus obtained, methods well known to those skilled in the art with or without pre-production of pre-composites are used.

  The autoclave process thus described is carried out at an elevated pressure of about 10-15 bar and a temperature of 130-145 ° C. for about 2 hours. For example, the vacuum bag method or the vacuum ring method according to EP 1 235 683 B1 is operated at about 200 mbar and 130-145 ° C.

  Advantageously, a vacuum laminator is used for the production of the photovoltaic module according to the invention. This vacuum laminator comprises a chamber that can be heated and evacuated, and laminated glass can be laminated within 30 to 60 minutes. A vacuum of 0.01-300 mbar and a temperature of 100-200 ° C., in particular 130-160 ° C., proves to be practical.

  Alternatively, the integrated laminate can be compressed at a temperature of 60-150 ° C. between at least one pair of rolls into a module according to the invention. This type of device is known for the production of laminated glass, and usually in the case of devices with two press tools at least one heating tunnel is used before or after the first press tool.

  The photovoltaic module according to the present invention can be used as a facade member, a roof plane, a sunroom cover, a soundproof wall, a balcony or a handrail member, or as a component of a window surface.

Measuring method
For the measurement of alkali titer , 3-4 g of a plasticizer-containing polyvinyl acetal film was dissolved in 100 ml of a mixture of ethanol / THF (80:20) with a magnetic stirrer overnight. To this was added 10 ml of dilute hydrochloric acid (c = 0.01 mol / liter) followed by blanking with a solution of tetrabutylammonium hydroxide (TBAH) in 2-propanol (c = 0.01 mol / liter) using Titroprozessor. In contrast, potentiometric titration was performed. This alkali titer is calculated as follows:
Alkali titer = HCl ml per 100 g sample = (TBAH blank by sample weight in grams-consumption of TBAH sample x 100).

The volume resistance of the sheet is measured according to DIN IEC 60093 after the sheet has been conditioned under the above conditions for at least 24 hours at the defined temperature and ambient humidity (23 ° C. and 85% rLF). To carry out this measurement, a Typ 302 132 plate electrode from Fetronic GmbH and an ISO-Digi 5kV resistance measurement device from Amprobe were used. The test voltage was 2.5 kV, and the standby time from application of the test voltage to measurement value detection was 60 seconds. In order to ensure sufficient contact between the flat plate of the measuring electrode and the sheet, its surface roughness Rz should not be greater than 10 mm when measured according to DIN EN ISO 4287, i.e. The original surface must be smoothed by thermal effects before resistance measurement.

The polyvinyl alcohol content and polyvinyl alcohol acetate content of the polyvinyl acetal were measured according to ASTM D 1396-92. The analysis of metal ion content was performed by atomic absorption analysis (AAS).

Measurement of the leaching behavior of PVB sheets at high humidity involves storing test strips in an atmosphere saturated with water vapor for 30 days. The absorption of water and the accompanying increase in polarity eliminates the plasticizer in the case of incompatible systems, so that this plasticizer gradually leaches out on the surface of the sheet in the form of a visible film or in the form of droplets. To do. In the case of compatible preparations, no plasticizer leaching can be observed after 30 days for this test strip, whereas this plasticizer leaching is frequently observed after 24 hours in the case of incompatible preparations. To occur. For the regulation of the atmosphere with high relative humidity (rF), a saturated aqueous solution with precipitates is produced from copper sulfate pentahydrate in a closed container, for example in a glass dryer. Above this solution, an equilibrium humidity of about 98% rF occurs at 23 ° C.

In order to measure the leaching behavior of PVB sheets in cold environments, sheet pieces of dimensions 30 × 10 cm are first conditioned for 24 hours in a climate of 23 ° C./23 rF and subsequently wound on a roll, which is steam-tight Alu-PE. Seal in a bag and store at a temperature of 5 ° C. for 1 week. After one week, the sheet is removed and the resulting plasticizer is examined.

  For the production of plasticized PVB sheets for testing the leaching behavior, the sheet material can be homogenized, for example in a roll device or an extruder.

Plasticizer release from PVB sheets is measured experimentally, for example, under conditions consistent with process performance in a vacuum laminator used for the production of photovoltaic modules. For this purpose, a round blank having a diameter of 60 mm is cut or manufactured from a sheet / sample with a thickness of 0.76 mm, and a weighed aluminum petri dish with a diameter of 65 mm (neoLab-aluminum dish, flat, 65 mm, Art .-Nr. 2-1605, mass of about 2.5 g). The sample is conditioned overnight in the petri dish in a 23 ° C./25% rF climate and subsequently left in a vacuum drying cabinet (Heraeus, Modell VTR 5022) at 150 ° C. and 1 mbar for 30 minutes. Prior to reweighing, the petri dish is freshly conditioned overnight at 23 ° C./25% rF. The rate of mass loss confirmed with respect to the initial mass of the sheet, expressed as a percentage, is defined as plasticizer release.

The softening temperature Tg of the partially acetalized polyvinyl alcohol is measured using differential scanning calorimetry (DSC) according to DIN 53765 using a heating rate of 10 K / min at a temperature interval of −50 ° C. to 150 ° C. Following the first heating gradient, a cooling gradient and a second heating gradient are performed. The state of the glass transition temperature was measured according to DIN 51007 for the measurement curve belonging to the second heating gradient. This DIN measurement point (Tg DIN) is defined as the cutting point of the horizontal line at half the step height in the measurement curve. This step height is defined by the vertical distance of both cut points at the center tangent at the baseline of the measurement curve before and after the glass transition.

The moisture or moisture content of the sheet is measured using the Karl-Fischer method after conditioning the sheet at 23 ° C. and 85% rF for at least 24 hours.

The cold flexibility of the sheet is simply evaluated by manual comparison of DIN A4 size sheet pieces at a storage temperature of 5 ° C.

Example The inventive sheet of this example fulfills the requirements normally imposed on PVB sheets for laminated safety glass or photovoltaic modules, which in particular are: high transparency or Absence of haze, slight inherent color and particularly low yellow value in this case, sufficient mechanical strength, low inherent odor, possible reduction of tackiness with the addition of normal anti-blocking agents, good and uniform on glass Adhesion and high volume resistance.

  Sheets were prepared according to the compositions in Tables 2-4 and tested for their suitability in the case of laminated safety glass or photovoltaic modules. Unless otherwise stated, all descriptions are given in mass% based on the total sheet. Exception: PVOH content is based on the amount of PVB resin. Hexamoll DINCH is a di-isononylcyclohexane-1,2-dicarboxylic acid from BASF SE and AEROSIL 130 is a commercial product from Evonik Degussa GmbH.

  Based on Comparative Example 1, the polyvinyl butyral having a degree of acetalization of 79% by weight, a PVA content of 20.0% by weight and a softening temperature of 75 ° C. is the usual mixing ratio for PVB sheets (74% by weight PVB, 26% by weight DINCH %) In a damp atmosphere (after 30 days) or in a cold environment (after 1 week), it was verified to partially release DINCH, ie exhibit exudation. Furthermore, this sheet only exhibits moderate cold flexibility.

  In Comparative Example 8, polyvinyl butyral having a degree of acetalization of 72.5% by weight, a PVA content of 26.4% by weight and a softening temperature of 81 ° C. uses a relatively small amount of DINCH as a plasticizer. Even when (PVB 80% by weight, DINCH 20% by weight), DINCH was partially released in a humid atmosphere (after 30 days) or in a cold environment (after 1 week), indicating that it showed exudation . Furthermore, this sheet has poor cold flexibility.

  A comparison between Examples 2 and 4 according to the invention and Comparative Examples 3 and 5 not according to the invention shows that moisture absorption is more plastic when using DINCH compared to test sheets made with 3G8. It shows that agent release is also reduced.

  Example 6 according to the invention is mixed with 26% by weight Hexamoll DINCH when using polyvinyl butyral having a degree of acetalization of 86% by weight, a PVA content of 13.0% by weight and a softening temperature of 67 ° C. A sheet with sufficient compatibility is produced, which sheet exhibits particularly low moisture absorption and low plasticizer release.

  Example 7 according to the invention comprises 24% by weight Hexamoll DINCH with the use of polyvinyl butyral having an acetalization degree of 84.7% by weight, a PVA content of 14.3% by weight and a softening temperature of 68 ° C. When mixing magnesium acetate-trihydrate, it affects the described properties of sufficient compatibility, especially slight moisture absorption and plasticizer release, without deteriorating the electrical volume resistance It proves that the enhanced alkali titer is adjusted without.

Example 8 according to the invention comprises 24% by weight of Hexamoll DINCH with the use of polyvinyl butyral having a degree of acetalization of 84.7% by weight, a PVA content of 14.3% by weight and a softening temperature of 68 ° C. In addition, the addition of pyrolytic SiO ₂ and the use of magnesium acetate-trihydrate has a minor effect on the described characteristics of sufficient compatibility, especially slight moisture absorption and plasticizer release Without, it is proved that the increased alkali titer is adjusted and at the same time the electrical volume resistance is further increased.

Example 9 according to the invention comprises 24% by weight Hexamoll DINCH with the use of polyvinyl butyral having a degree of acetalization of 84.7% by weight, a PVA content of 14.3% by weight and a softening temperature of 68 ° C. In addition, the addition of pyrolytic SiO ₂ further increases the electrical volume resistance without significantly affecting the compatibility, in particular the described characteristics of slight moisture absorption and plasticizer release. Prove that.

The sheet according to the invention is well suited for the production of photovoltaic modules based on this good insulating property. Furthermore, the sheets of Examples 7 to 9 according to the invention show a particularly low corrosivity for the sensitive functional layers of the photovoltaic modules due to their high alkalinity and / or the presence of pyrolytic SiO ₂ .

Table 2

Table 3

Table 4

Claims (11)

  60 to 90% by weight of polyvinyl acetal having a softening temperature Tg of less than 74 ° C. and 4 to 17 C atoms in the ester group as a plasticizer, based on the total weight of the sheet A plasticizer-containing sheet having at least one cyclohexanedicarboxylic acid ester having 10 to 40% by mass. The acetalization degree of the polyvinyl acetal, characterized in that it is 81 mass% or more, the plasticizer contained in the sheet according to claim 1, wherein. The plasticizer-containing sheet according to claim 1 or 2 , wherein the polyvinyl acetal has an acetate content of less than 5% by mass. The sheet is characterized by having a plasticizer release of less than 4 wt%, a sheet containing a plasticizer of any one of claims 1 to 3. The plasticizer-containing sheet according to any one of claims 1 to 4 , wherein polyvinyl butyral is used as the polyvinyl acetal. Use of a plasticizer-containing sheet according to any one of claims 1 to 5 for producing a laminated glass, a windshield or a photovoltaic module.   a) a transparent front cover, b) one or more light-sensitive semiconductor layers, c) a sheet based on polyvinyl acetal containing at least one plasticizer, and d) a back cover. In the photovoltaic module having a laminate, the plasticizer-containing sheet is composed of 60 to 90% by mass of polyvinyl acetal having a softening temperature Tg of less than 74 ° C. and an ester group as a plasticizer with respect to the total mass of the sheet. A photovoltaic module comprising 10 to 40% by weight of at least one cyclohexanedicarboxylic acid ester having 4 to 17 C atoms therein. 8. The light according to claim 7 , characterized in that the plasticizer-containing sheet a) based on polyvinyl acetal contains a metal salt of a carboxylic acid having 1 to 15 carbon atoms as a basic compound. Electromotive force module. Wherein the free plasticizers, sheet based on polyvinyl acetal, characterized in that it contains SiO ₂ 0.001 to 5% by weight, according to claim 7 or 8 photovoltaic module according. One or more light-sensitive semiconductor layers b) are provided on the transparent front cover a) or the back cover d) and are mutually connected by at least one sheet c) containing a plasticizer and based on polyvinyl acetal. characterized in that it is bonded to the photovoltaic module according to any one of claims 7 to 9. Semiconductor layer b of the light sensitive) is embedded between two sheets c), the characterized in that is bonded to the cover a) and d), any one of claims 7 to 10 The photovoltaic module as described.